Engine Controls - Basic Testing - 3.3L CNG: Introduction

NOTE: For diagnostic procedures on systems used in common with gasoline powered vehicles, proceed to BASIC TESTING - 3.3L GASOLINE article in the ENGINE PERFORMANCE section.

The following diagnostic steps can help prevent overlooking a simple problem. Also use this article to begin diagnosis for a no-start condition. The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under conditions in which the problem reportedly occurs.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most driveability and no-start problems are not related to computerized engine control systems, but are simple mechanical, electrical, fuel or vacuum related faults. Most engine control problems are the result of mechanical breakdowns, poor electrical connections, or damaged or misrouted vacuum hoses. Before condemning the computerized engine control system, perform each test listed in this article.

NOTE: All voltage tests should be performed using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance unless stated otherwise in testing procedures.